Studies involving in vivo regulation and replication of the bacterial chromosome have suggested models of DNA replication in which the replication complex is associated with the membrane. Experiments designed to establish such a relationship have focused on demonstrating a physical association between the bacterial chromosome and its cellular membrane. While the majority of these studies support the thesis that the bacterial chromosome is in association with the cellular membrane, very little information is available concerning the physical or physiological nature of this attachment. It is the purpose of the following proposal to study the role of the bacterial membrane in the replication of the E. coli chromosome. To accomplish this, we propose to alter the composition and structure of the bacterial membrane and study the resulting effect(s) on chromosomal replication. This project will combine in vivo and in vitro studies to examine the interaction of the membrane and replication complex, and will utilize conditional lethal, temperature- sensitive DNA mutants, mutants defective in membrane biosynthesis and in vitro DNA replication.